The present application relates generally to the field of thiazolide compounds. In particular, the application relates to alkylsulfonyl-substituted thiazolide compounds.
Hepatitis B Virus (HBV) and Hepatitis C Virus (HCV) are major public health problems, causing more than an estimated 500 million chronic infections worldwide (Chen and Morgan, 2006; Lavanchy, 2004). Both viruses are a source of significant progressive liver disease, and are the major risk factors for nearly all cases of primary hepatocellular carcinoma (Chen and Morgan, 2006; Lavanchy, 2004; Wong and Lok, 2006). Licensed standards of care for both viral infections, while effective in many cases, are sub-optimal and do not result in virologic or clinical ‘cures’ in most individuals (Wong and Lok, 2006). The development of drug-resistance in HBV, including strains carrying resistance to multiple licensed agents is an emerging clinical problem, and drug-resistance for future HCV therapies is predicted to be a significant clinical issue (Tomei et al., 2005; Tong et al., Yim et al., 2006).
Thiazolide compounds such as nitazoxanide (NTZ) are anti-infective and possess activity against anaerobic bacteria, protozoa and viruses (Fox et al., 2005; Pankuch and Appelbaum, 2006; Rossignol et al., 2006a; Rossignol and El-Gohary, 2006). Originally developed as a treatment of intestinal protozoan infections, the antiviral properties of NTZ were discovered during the course of its development for treating cryptosporidiosis in patients with acquired immune deficiency syndrome (AIDS). NTZ is marketed in the United States for treating diarrhea and enteritis caused by Cryptosporidium spp or Giardia lamblia in adults and children down to 12 months of age (Alinia®, Romark Laboratories, Tampa, Fla. USA). Clinical trials have demonstrated effectiveness of NTZ in treating diarrhea and enteritis associated with enteric protozoan infections caused by Cryptosporidium spp, G. lamblia, Entamoeba histolytica and Blastocystis hominis (Amadi et al., 2002; Oritz et al., 2001; Rossignol et al., 2001, 2005, 2006b). Recent randomized double-blind clinical trials have demonstrated effectiveness of NTZ in treating Clostridium difficile colitis in adults, rotavirus gastroenteritis in young children, and rotavirus and norovirus gastroenteritis in adults (Musher et al, 2006; Rossignol et al, 2006a; Rossignol and El Gohary, 2006). The mechanism of action of NTZ against anaerobic organisms is attributed to interference with pyruvate:ferredoxin oxidoreductase (PFOR) enzyme-dependent electron transfer reactions, which are essential for anaerobic energy metabolism (Hoffman et al., 2006). Its mechanism of antiviral activity has not been fully elucidated.
Following oral administration of a 500 mg tablet, NTZ is partially absorbed from the gastrointestinal tract and rapidly hydrolyzed in plasma to form its active circulating metabolite, tizoxanide (TIZ). NTZ is not detected in plasma. Maximum serum concentrations of TIZ, reach approximately 10 μg/mL (37 μM) (Stockis et al., 2002) following oral administration of one 500 mg NTZ tablet (Alinia®) with food. TIZ is glucurono-conjugated in the liver and excreted in urine and bile. Approximately two-thirds of an oral dose pass through the intestinal tract and is excreted in feces as TIZ (Broekhuysen et al., 2000). The elimination half-life of TIZ from plasma is approximately 1.5 hours. TIZ does not inhibit cytochrome P450 enzymes, and therefore, no drug-drug interactions are expected (Broekhuysen et al., 2000; Stockis et al., 2002). The most commonly reported side-effects in clinical trials include mild abdominal pain, headache, diarrhea and nausea, which occur at rates similar to those reported for patients receiving placebo. While most of the clinical experience with NTZ has involved 3 to 14 days of treatment, continual use of the drug for periods as long as 4 years has been evaluated in patients with AIDS-related cryptosporidiosis without any significant drug-related adverse events (Fox et al., 2005; Rossignol, 2006).
Here, results of studies characterizing the activities of NTZ, TIZ and other new thiazolides are presented. In particular, the antiviral activity of 2-benzamido-5-alkylsulfonyl-thiazoles is demonstrated.